Method of making alloys.



I UNITE STATES PATENT OFFICE.

METHOD OF MAKING ALLOYS.

SPECIFICATION forming part of Letters Patent No. 696,244, dated March 25, 1902. I

Application filed Novemher l5, 1 8 9 9 Serial No. 737,055. (No specimens.)

To all whom it may concern.-

Be it known that I, EDWARD KELLER, a citizen of the United States, and a resident of Baltimore, in the State of Maryland, have discovered certain new and useful Improvements in the Method of Preventing and Reducing Concentration and Dispersion of Im- -mentation and observation that foreign metals, metalloids, &c., held in'solution in the solvent metal tend as the metal freezes or solidifies to accumulate or predominate at cer tain centers or zones. This tendency is entirely independent of any gravity separation occurring while the mass is in its molten or liquid condition and results in a casting the several parts of which vary in the relative proportions of their constituent elements. This unequal distribution of the elements of a casting has been termed segregation, which term I shall adopt herein, and it is obvious that as a result of it castings designed for strength are liable to be Weak in certain portions without the possibility of detection" until the weakness is developed by fracture. So, too, should the casting-an ingot, for instance-be designed for assaying, samples taken from any one portion will not give a true indication of the relative proportions of the metals in the entire mass, but may assay either above or below the average, depending upon whether the impurities have accumulated or not at the particular point where the sample is taken. The metal, metalloids, &c., which occasion the phenomenon of segregation I shall herein term impurities, although any one or more of them may be valuable, if not the most valuable constituent or constituents of the mass, even though existing in relatively small quantities.

In the most prominent and general form of segregation the impurities tend toward the portions of the metal last to solidify, while in other forms of segregation the opposite effect is observed-4. e., the impurities tend toward those portions of the mass the first to solidify. In either case the tendency to segregate may result in a series of zones having varying proportions of the constituent elements of the mass.

I have discovered that segregation may be greatly reduced by combining the solvent metal and impurities in such proportions that the solvent metal will be saturated with the impurities when at the freezing or solidifying temperature. In other words, I have observed that metals at freezing or solidifying temperature have a certain capacity for holding in solution a given quantity of impurities without tending to segregate. Subsaturation I have discovered causes a segregation toward the center of solidification and supersaturation causes a segregation in the opposite direction.

Each metal, metalloid, &c., has a definite point of saturation in every solvent metal. The point of saturation becomes variable when more than one element is dissolved. Thus the saturation-points for a number of elements are interdependent. From this it follows that the saturation-point of one element is lowered by the solution of one or more other elements, and when the solvent is subsaturated with one element or with a number of elements and segregation toward the center of solidification takes place the addition of the same element or of other elements in quantity suffic'ient to charge the solvent to the saturation-point at solidifying temperature will retard, reduce, or prevent segregation.

In case of segregation toward the portions of the mass first to solidify because of supersaturation some of the impurities must be eliminated or additional purer solvent metal added to give a saturated solution at the freezing temperature.

The addition to be made to the mass to bring it to the saturation-point at the freez ing temperature must be determined empiricallyfor instance, by analysis of samples taken from certain portions of sample castings, which when they show segregation and the degree of segregation toward the center of solidification indicate subsaturation and the quantity of impurity to be added to bring the mass up to the point of saturation.

Obviously in the practical application of my discovery experience in handling metals of a certain grade where segregation occurs will enable the operator to' add an impurity in the first instance without sampling, which will benefit the solvent metal in its industrial application and at the same time reduce or prevent segregation due to the impurities which already exist and cannotbe entirely eliminated or which have been added to produce a desired alloyor combination of metals.

Many practical examples wherein segregation has been greatly lessened or prevented for all practical purposes might be given; but the following will answer for illustrative purposes, viz: Refined copper was the metal employed, and from a batch of this metal a block was cast of convenient size rectangular in shape and samples were taken vertically and approximately through the center of solidification or last portion of the mass to solidify. The analysis was made of each inch in vertical height, starting at the top, and the following tables are based on the percentage of two impurities-silver and goldper ton.

Th us:

Ag oz. Au oz. per per ton. ton.

1; inch 85.0 F11 st inch inch 0.28 Second inch. 89.5 0.24 Third inch 87.0 0.24 Fourth inch 80.1 0.26 Fifth inch 81.0 0.22

This shows a segregation toward the center of solidification, which is a point near the vertical center and toward the top of the mass. By adding a small quantity of lead analysis showed the following results:

Ag 07 An 07 per per ton. ton

First inch 86.0 0.22 Second inch 85.8 0.24 Third inch 85.3 0.24 Fourth inch 86.2 0.24 Fifth inch 85.7 0.22

By adding zinc the following results were obtained:

Fifth inch By adding nickel the following results were obtained:

Ag 0/ Au oz. Nickel. per per ton. ton.

Per ct. First inch 0.40 88.0 0.20 Second inc 0.30 87.1 0.21 Third inch 0.38 85.5 0.20 Fourth inch. 0.35 87.8 0.28 0.30 87.0 0.22

The same grade of copper as the above refined copper when containingasmall amount of sulfur becomes what is known as blister copper, which shows segregation to a much more marked degree, yet on adding more sulfur this segregation may be reduced or even prevented, as shown by the following illustrations:

A copper containing about 0.5 per cent. of sulfur shows the following segregation for silver and gold:

Ag oz. Au oz. per per ton. ton.

F11 st inch 90.2 0.20 Second inch 08.1 0.20 Third inch 102.3 0.28 Fourth inch 77.4 0.20 Fifth inch 78.3 0.26

On increasing the tenor of sulfur to about 0.9 per cent. the segregation is shown to be reduced as follows:

It appears, therefore, that by adding a small quantity of an impurity to the solvent metal when segregation toward the center of solidification occurs the tendency to segregate in this direction is lessened anduniformity of the mass greatly increased. The amount to be added, as before stated, must be determined empirically inasmuch as it will vary with the aggregate impurities contained in the solvent metal.

Having thus described my discovery, what I claim is- 1. The method of reducing segregation in cast metal, which consists, first, in determining by analysis of a casting, whether segregation occurs toward or away from those portions of the casting first to solidify, and secondly in combining with the remelted metal or other portion of the same batch of metal when in a fluid condition, a substance forwhich consists first in ascertaining whether 7 segregation occurs toward or away from those portions of the casting first to solidify,

secondly in varying the proportion of foreign soluble material in the mass in accordance with-the previously ascertained direction and degree of segregation to maintain a homogeneity of the mass at the solidifying or freezing temperature and finally casting the treated molten metal; substantially as described.

EDWARD KELLER.

Witnesses:

JOHN JOHNS, THOMAS J. RIGNEY. 

